Supermarkets are banking on a sales surge this Halloween, with one City analyst calculating shoppers could spend up to £460m on fancy dress, food and decorations. The celebration is the UK’s second-biggest party night after New Year’s Eve, say analysts at Conlumino, and some supermarkets expect a sales boost of up to 20% this year because the event falls on a Saturday. Halloween has grown in popularity in the UK and easily accounts for more spending than bonfire night. Parties were once focused on children, but Watson said adults were increasingly prepared to dress up. Asda said it had more than tripled its stocks of costumes this year and bought nearly 60% more makeup as it expected Halloween sales across all categories to rise by 20%. Sainsbury’s said it had bought 30% more adult costumes than last year and 22% more non-food Halloween-related products.